High power circuit breaker applications typically employ electro-mechanical solenoids to physically open and close a circuit breaker. The electro-mechanical solenoid that opens the breaker is referred to as the "open" coil. The solenoid that physically closes the circuit breaker is referred to as the "close" coil. In prior art circuit breaker applications, a third coil, commonly referred to as the "Y" coil is employed to inhibit an additional close signal to the close coil. A "Y" coil combined with its supporting circuitry is commonly referred to as an "anti-pump" circuit.
American National Standards Institute (ANSI) standards C37.09-1979 and C37.11-1979 specify that a circuit breaker should close only once in response to any one close signal. A circuit breaker which meets this specification is said to have anti-pump. Under these ANSI standards, if a close signal is applied to a circuit breaker and subsequently maintained or held, the circuit breaker shall not close again until the close signal is first removed and a new close signal applied. This rule holds even if the circuit breaker opens while the initial close signal is being held. In such a case, the close signal must be removed before the breaker is permitted to re-close.
Prior art circuit breaker applications attempted to satisfy the ANSI standards by designing the electro-mechanical "Y" coil to "lock out" redundant close signals that are received prior to the release of a previous close signal. However, electro-mechanical coils, including those employed as "Y" coils are subject to bounce and chatter. Bounce in the "Y" coil is particularly troublesome with respect to the anti-pump standards in that it can cause an activation signal to be inadvertently transmitted to the close coil. For example, due to the bounce inherent in all electro-mechanical coils, which is amplified by the closing-force shock of the breaker itself, a "Y" coil may transmit an activation signal to the close coil when the close coil should be electrically locked out. Such an inaccuracy in the operation of the "Y" coil violates the ANSI anti-pump standards. Furthermore, this deficiency in the electro-mechanical "Y" coil can cause the breaker to re-close during interruption, which can lead to circuit breaker failure.
Therefore, there is a need for a circuit breaker control system that provides accurate and reliable anti-pump control.